President Trump Being Investigated For Obstruction

After Mueller was appointed last month, Trump tweeted: "This is the single greatest witch hunt of a politician in American history".

The news did not go unnoticed by the Commander-in-Chief who - as is style - took to Twitter Thursday morning to blast the report as "phony" and accused investigators of pursing it only because they found "zero proof" of Russia-Trump collusion.

Robert Mueller, the special counsel in charge of investigating allegations of collusion between the Russian government and the Donald Trump presidential campaign, has requested to interview several high-ranking officials about whether the president sought to end an Federal Bureau of Investigation probe, unnamed sources said.

It cited five people briefed on the requests by Mueller's team who spoke on condition of anonymity.

A spokesperson for President Trump's personal attorney Marc Kasowitz said in response to the Post's report: "The FBI leak of information regarding the president is outrageous, inexcusable and illegal".

Comey had told Congress that the FBI was investigating possible links between Trump campaign officials and the Russian government, which USA intelligence agencies accuse of hacking the Democratic National Committee's emails past year in a bid to influence the election against Hillary Clinton.

According to one source, Mueller sees the obstruction claims as more than just "he said, he said" between Trump and Comey.

Trump was forced to fire Flynn in February after he misled the White House about his contacts with Russian officials previous year as a member of Trump's transition team. The Post's sources said that changed following Comey's firing.

Trump had received assurances from then-FBI Director James Comey starting in January that he was not personally under investigation.

The White House has said the president "has never asked Mr Comey or anyone else to end any investigation, including any investigation involving General Flynn".

While a sitting president is unlikely to face criminal prosecution, obstruction of justice could form the basis for his impeachment in Congress.